src/hotspot/share/opto/compile.cpp

*** 2182,2191 ****
--- 2182,2208 ----
      }
    }
    return true;
  }
  
+ // Remove edges from "root" to each SafePoint at a backward branch.
+ // They were inserted during parsing (see add_safepoint()) to make
+ // infinite loops without calls or exceptions visible to root, i.e.,
+ // useful.
+ void Compile::remove_root_to_sfpts_edges() {
+   Node *r = root();
+   if (r != NULL) {
+     for (uint i = r->req(); i < r->len(); ++i) {
+       Node *n = r->in(i);
+       if (n != NULL && n->is_SafePoint()) {
+         r->rm_prec(i);
+         --i;
+       }
+     }
+   }
+ }
+ 
  //------------------------------Optimize---------------------------------------
  // Given a graph, optimize it.
  void Compile::Optimize() {
    TracePhase tp("optimizer", &timers[_t_optimizer]);
  
*** 2242,2251 ****
--- 2259,2272 ----
      print_method(PHASE_INCREMENTAL_BOXING_INLINE, 2);
  
      if (failing())  return;
    }
  
+   // Now that all inlining is over, cut edge from root to loop
+   // safepoints
+   remove_root_to_sfpts_edges();
+ 
    // Remove the speculative part of types and clean up the graph from
    // the extra CastPP nodes whose only purpose is to carry them. Do
    // that early so that optimizations are not disrupted by the extra
    // CastPP nodes.
    remove_speculative_types(igvn);
*** 3246,3259 ****
            if (use->is_Proj() && p != use && use->as_Proj()->_con == p->_con) {
              proj = use;
              break;
            }
          }
!         assert(proj != NULL, "must be found");
          p->subsume_by(proj, this);
        }
      }
      break;
    }
  
    case Op_Phi:
      if (n->as_Phi()->bottom_type()->isa_narrowoop() || n->as_Phi()->bottom_type()->isa_narrowklass()) {
--- 3267,3282 ----
            if (use->is_Proj() && p != use && use->as_Proj()->_con == p->_con) {
              proj = use;
              break;
            }
          }
!         assert(proj != NULL || p->_con == TypeFunc::I_O, "io may be dropped at an infinite loop");
!         if (proj != NULL) {
            p->subsume_by(proj, this);
          }
        }
+     }
      break;
    }
  
    case Op_Phi:
      if (n->as_Phi()->bottom_type()->isa_narrowoop() || n->as_Phi()->bottom_type()->isa_narrowklass()) {